Allan,
I opened my laptop this morning and Avira Antivirus did not show up in my Control Panel - Programs. I then restarted my laptop, and it appears Avira Antivirus is gone! THANK GOODNESS. What an insidious product! I went to the Avira support page and ended up by following the steps to "Removing Avira Antivirus in Windows 10 Manually". A somewhat complicated procedure, but hopefully it has finally worked.
Thanks for your help/suggestion.